[SOLVED] Re: labelling root file system (RELENG_8)

Jeremy Chadwick freebsd at jdc.parodius.com
Wed Jun 8 16:55:18 UTC 2011

On Wed, Jun 08, 2011 at 07:40:03PM +0300, Andriy Gapon wrote:
> on 08/06/2011 19:26 Jeremy Chadwick said the following:
> > I have the exact same question except not with regards to labels but
> > toggling TRIM capability on the root filesystem.
> > 
> > - Start system
> > - At loader, boot single-user (option 4)
> > - At prompt choose /bin/sh
> > - mount -a
> I think that this is a culprit.

I'll try removing this step.

> > - tunefs -t enable /dev/ada0s1a --- fails
> Shouldn't you have / mounted r/o here?
> BTW, AFAIR, *re*-mounting root read-only won't help; it needs to have never been
> mounted r/w.

I'm a little confused by this sentence, so my apologise in advance.  /
is mounted read-only in single-user by default.  Did you mean I should
make it r/w by doing "mount -u -o rw /" ?  I may have omitted this step.

I will re-verify the exact procedure and exact steps in a moment, and
reply here.

> > - sysctl kern.geom.debugflags=16
> > - tunefs -t enable /dev/ada0s1a --- works
> > - tunefs -p /dev/ada0s1a -- shows TRIM enabled
> > - reboot
> I think that at this step your superblock on disk gets re-written with its copy in
> memory which has never been updated.  But not sure.

Hmm, I sure hope that isn't the case.  That would mean the only time a
person can use tunefs on a root filesystem is when they either do it
manually during the FreeBSD installation (adding "-t" to the list of
newfs flags in the filesystem creation UI), or if they boot off of some
other medium (USB flash drive, CD, PXE, etc.).

| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                   Mountain View, CA, US |
| Making life hard for others since 1977.               PGP 4BD6C0CB |

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